This invention starts from a stop-start device for a motor vehicle according to the features of the invention.
Stop-start devices have been fitted in motor vehicles, in which the engine is switched off upon actuation of a stop button insofar as the road speed has fallen below a value of, for example, 5 km per hour. Furthermore stop-start devices are known, in which the engine is automatically switched off with a given delay time after a stoppage of the motor vehicle. Such devices are intended to save fuel and prevent an exhaust of poisonous carbon monoxide. On the other hand a switching off of the engine which, as is known drives the generator of the vehicle, of course affects the charge condition of the vehicle battery especially if consuming devices with a high current consumption are switched on. The known devices have therefore been developed in a way that in order to reduce the current consumption the rear window heating installation is switched off at a standstill of the engine. But this principle cannot applied to all other consuming devices in a motor vehicle, because the operational reliability would thereby be impaired.
The invention is based on the problem of developing a stop-start device of the known kinds in a way that an appropriate compromise is achieved between saving of fuel and a charge condition of the battery, which is sufficient for functionally important consuming devices, and further operating conditions in the motor vehicle.